1. Technical Field of the Invention
The present invention relates to data communications and in particular to improving performance of multiple network multiple protocol communication using a shared medium.
2. Description of the Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11b, IEEE 802.11g, IEEE 802.11a, Bluetooth, IEEE 802.16e, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof. Wireless communication devices exploit electromagnetic wave propagation to transmit data. Such communication devices include a radio receiver and/or a radio transmitter.
The radio transmitter usually includes a data modulation stage, one or more frequency conversion stages, and a power amplifier coupled to the antenna. The data modulation stage converts (modulates) raw data bits into baseband signal in accordance with a particular wireless communication standard. The frequency conversion stages convert baseband signal into a radio frequency (RF) signal. The power amplifier amplifies the RF signal and an antenna radiates RF signal as an electromagnetic field.
The radio receiver is coupled to an antenna and usually includes low noise amplifier, one or more frequency conversion stages, one or more filtering stages and a data recovery stage. The antenna converts electromagnetic field into an electrical RF signal, the low noise amplifier amplifies the electrical RF signal, the frequency conversion stages convert RF signal into a baseband signal, the filtering stages attenuate all unwanted frequency components and the data recovery stage recovers (demodulates) raw data from the filtered signal in accordance with a particular communication standard.
The electromagnetic field radiated at the receive antenna is inversely proportional to the distance from the transmit antenna. The electrical RF signal produced by the antenna is coupled with the noise signal caused by the random thermal motion of the electrons. This noise may cause errors in the data recovery process. The probability of such error depends on the signal to noise ratio (SNR) and the type of modulation used in the data transmission. The higher the SNR ratio, the lower the probability of the bit error. The reliability of the wireless link is often measured by the bit error rate (BER) or packet error rate (PER).
Wireless standards often allow transmitter to use more than one way to modulate the raw data. For example wireless communication devices that are compliant with 802.11g standard can communicate with each other using data rates of 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48 and/or 54 Mbps (megabits per second). Usually the higher the data rate the higher the SNR needed to achieve equivalent BER or PER.
To maintain a reliable data connection at the highest possible data rate the transmitter usually employs a dynamic transmission adaptation algorithm. Such algorithm usually reduces the data rate for wireless communication when number of unsuccessful attempts to transmit the packet reaches a certain threshold. In an environment where the thermal noise is the only source of demodulating errors this algorithm converges to the highest data rate supported by the wireless link.
As is known, differing standards sometimes use the same communication medium (e.g., allocated radio frequency spectrum, wired connections, etc.) due to a finite amount of communication medium. For example, both Bluetooth and IEEE 802.11g use the 2.4 GHz spectrum. As long as communication systems that are compliant with differing standards that share a communication medium do not physically overlap, the systems operate without interference from each other. However, if the communication systems do physically overlap, they might interfere with each other, degrading the performance of both systems. For example, if a Bluetooth pico-net physically overlaps with an IEEE 802.11b local area network, simultaneous use of the 2.4 GHz spectrum might cause interference that can cause both transmissions to fail.
Further a single device can be capable of operating in two modes (e.g. Bluetooth and WLAN or WLAN & WiMax) such that operation of the device in one mode could preclude simultaneous operation in the other mode, particularly if one or more shared circuit components are used to implement these two modes of operation. For instance, if the device is operating in a Bluetooth mode, 802.11g transmissions directed to the device could fail and vice versa.
For transmission with the same amount of data, the probability of the overlapping medium use is higher for lower data rates as such packets require longer time to transmit. For the cases where transmission failed due to the interference from another network using the same medium or due to transmissions directed to a multimode device that uses shared circuit components, the regular dynamic transmission adaptation algorithm employed by the transmitter results in lowering the data rate, increasing the packet transmission time thus further increasing the probability of the medium access collisions. Other disadvantages of the prior art will be apparent to one skilled in the art when presented the disclosure herein.